1. Field of Invention
The present invention relates to a diagnostic system and a method for operating the diagnostic system. More particularly, the present invention relates to a diagnostic system for fault detection in a semiconductor process and an operating method thereof.
2. Description of Related Art
Currently, in the semiconductor process, a metrology process for checking the process performance is performed every several runs. The metrology process includes several measurement items, such as thickness, depth, uniformity, critical dimension, defect count, film quality, etc. When the result of the metrology process shows that the process performance is abnormal, the users will check or re-tune the tool that is used to perform the process and modify the process recipe in order to adjust the process performance to be normal.
However, the metrology process is not performed for every process run of each wafer since it takes long time to perform the metrology process. Hence, the result of the metrology process does not real-time reflect the timing at which the process performance starts to change due to the variation of the process environment. Conventionally, the fault detection for diagnosing the variation of the process parameters of the tool during the process is performed is set by referring to the historic process parameters of the tool without relating to the post process measurement result of the metrology process. Nevertheless, different combination of the variations of the process parameters will lead to different process performance. Some combination of the variation of the process parameters may not affect the process performance and some may impact the process performance. Therefore, it is possible that the fault diagnostic happens since the fault detection is only based on the current variation of the process parameters and the historical process parameters.